Current therapy of human immunodeficiency virus (HIV) infection is imperfect. Drug toxicities, resistance, and the emergence of syncytium- inducing isolates all limit the effectiveness of available therapies. New therapies are therefore urgently needed. Catalytic RNA molecules (ribozymes) possess sequence-specific endoribonuclease activity. Several groups have reported preliminary in vitro evidence for activity of anti- HIV ribozymes targeted against gag, pol, vif, tat, rev, and the conserved 5' leader sequence of HIV mRNA. In most cases, these ribozymes were designed on the basis of sequence data for molecular clones of highly passage strains of HIV-1. TO date, activity of anti-HIV ribozymes against low-passage clinical isolates of HIV-has not been reported. The sequence heterogeneity of HIV-1 isolates and the rapid divergence of quasispecies of HIV-1 upon in vitro passage make it essential to validate these preliminary results with clinical isolated of the virus. We propose to design and test ribozymes targeted against HIV-1 sequences derived from clinical isolates of infected individuals. Ribozymes designed by (projects 1 and 9001 of this application) will be tested against a panel of low-passage clinical isolates. Both gene therapy and liposome systems will be used to deliver ribozymes or ribozyme expression vectors to T-cell lines and peripheral blood mononuclear cells (PBMC). Expression of ribozymes in PBMC will be confirmed by RT-PCR in situ. The emergence of ribozyme "escape" mutants will be investigated by analyzing ribozyme target sequences in viruses recovered from these cultures.